Geocordinates in new Job via API

I already have coordinates for jobs so when I add via the API, they are overridden by a search on the address.

If I make the address invalid eg

"job_address": "crap address ",
"lng":171.34470269,"
"lat":-42.09278384,

...it defaults to the head office location

"lng": 174.7644881,
"lat": -36.8508827,

What is the usage of lat+lng paramaters in the job create API?